Make base::PendingTask support ConvertableToTraceFormat

base/pending_task.h

Index: base/pending_task.h
diff --git a/base/pending_task.h b/base/pending_task.h
index 5761653397e0e5d011522f56e786fa1cbbbcc373..81ea2e953f38576e55ea255266e24980969205f8 100644
--- a/base/pending_task.h
+++ b/base/pending_task.h
@@ -5,12 +5,15 @@
 #ifndef BASE_PENDING_TASK_H_
 #define BASE_PENDING_TASK_H_
 
+#include <memory>
 #include <queue>
 
 #include "base/base_export.h"
 #include "base/callback.h"
 #include "base/location.h"
+#include "base/macros.h"
 #include "base/time/time.h"
+#include "base/trace_event/trace_event_impl.h"
 #include "base/tracking_info.h"
 
 namespace base {
@@ -18,6 +21,21 @@ namespace base {
 // Contains data about a pending task. Stored in TaskQueue and DelayedTaskQueue
 // for use by classes that queue and execute tasks.
 struct BASE_EXPORT PendingTask : public TrackingInfo {
+  // A thread-safe copy of a PendingTask's info required by tracing.
+  class TracingInfo : public trace_event::ConvertableToTraceFormat {

[caseq, 2016/09/29 22:46:37]

Why does it have to be nested class of PendingTask? This could as well be
somewhere else.

[gab, 2016/10/03 15:18:58]

Good point, I'll move it when we achieve overall consensus on what this CL is
doing.

+   public:
+    TracingInfo(const tracked_objects::Location& posted_from);
+    ~TracingInfo() override;
+
+    // Overridden from trace_event::ConvertableToTraceFormat:
+    void AppendAsTraceFormat(std::string* out) const override;
+
+   private:
+    const tracked_objects::Location posted_from_;
+
+    DISALLOW_COPY_AND_ASSIGN(TracingInfo);
+  };
+
   PendingTask(const tracked_objects::Location& posted_from,
               Closure task);
   PendingTask(const tracked_objects::Location& posted_from,
@@ -32,6 +50,8 @@ struct BASE_EXPORT PendingTask : public TrackingInfo {
   // Used to support sorting.
   bool operator<(const PendingTask& other) const;
 
+  std::unique_ptr<trace_event::ConvertableToTraceFormat> GetTracingInfo() const;

[caseq, 2016/09/29 22:46:37]

ditto.

[gab, 2016/10/03 15:18:58]

Acknowledged.

+
   // The task to run.
   Closure task;